Present article reports the effect of humic substances on the availability of rock phosphate to crop growth.Water culture experiments for wheat,tomato and rice were carried nut with both ordinary rock phosphate and radioactive rock phosphate as phosphate sources.Experiments showed nn evidence that the addition of sodium humate gave beneficial effect on the availability of phosphate from rock phosphate to crop growth.However,the stimulating effect of sodium humate on root growth can be observed in all cases.